Which form of heat transfer travels in all directions?

Thermal radiation is the correct answer because it refers to the transfer of heat energy through electromagnetic waves, which can propagate through a vacuum as well as through various media. Unlike conduction, which requires direct contact between materials, or convection, which involves the movement of fluids (liquids or gases) and transfers heat through circulation, thermal radiation does not rely on a medium to transfer heat. This allows it to travel in all directions from the source, enabling it to reach objects that are not in direct contact with the heat source. In practical scenarios, thermal radiation is responsible for the warmth felt from the sun or a fire, as the heat radiates outwards without needing any material in between to facilitate that transfer.